Level vial construction

ABSTRACT

A LEVEL VIAL FOR USE IN CONNECTION WITH A LEVEL INSTRUMENT FOR DETERMINING ANGULAR RELATIONSHIPS. THE LEVEL VIAL CONSISTS OF A BODY WHICH CONTAINS A BORE DESIGNED TO SERVE AS A BUBBLE CHAMBER. A CORE MEMBER IS SECURED WITHIN THE BORE OF THE VIAL BODY IN A PREDETERMINED POSITION. AFTER A QUANTITY OF FLUID IS INTRODUCED INTO THE BORE AND HERMETICALLY SEALED THEREIN TO PROVIDE A BUBBLE IN THE BORE OR CHAMBER, THE CONFIGURATION AND LOCATION OF THE CORE MEMBER SECURED WITHIN THE BORE SERVES, IN COOPERATION WITH THE SURFACES DEFINING THE BORE OR CHAMBER, TO CONTROL THE POSITION OF THE BUBBLE WITHIN THE VIAL IN ACCORDANCE WITH THE ANGULAR DISPOSITION OF THE LEVEL VIAL. D R A W I N G

June 8, 1971 J. A. BALINT 3,583,073

LEVEL, VIAL CONSTRUCTION Filed June 21, 1968 F IGI 2 2 l3 ZO IO INVENTORJOSEPH A. BALINT BY M, 27mg 0%!- ATTORNEYS United States Patent @1 Int.Cl. G01c 9/24 US. Cl. 33-411 12 Claims ABSTRACT OF THE DISCLOSURE Alevel vial for use in connection with a level instrument for determiningangular relationships. The level vial consists of a body which containsa bore designed to serve as a bubble chamber. A core member is securedwithin the bore of the vial body in a predetermined position. After aquantity of fluid is introduced into the bore and hermetically sealedtherein to provide a bubble in the bore or chamber, the configurationand location of the core member secured Within the bore serves, incooperation with the surfaces defining the bore or chamber, to controlthe position of the bubble within the vial in accordance with theangular disposition of the level vial.

The level industry has been confronted with problems relating to thehigh degree of skill required in the final production phases of levelinstrument manufacture includ ing relatively slow assembly techniques.This problem was approached and solved by the development of a new levelvial and a means for assembling the vial to a suitable frame requiringminimal skills throughout the manufacturing and assembly processes andwhich materially reduce the time involved in producing a completed levelinstrument. The new level vial and means for assembling the vial to aframe is set forth in the patent to Donald E. Wright, 3,311,990, issuedApr. 4, 1967, and entitled Level.

The present invention is aimed at a level and vial construction whichwill produce substantial reduction in the cost of manufacture of levelinstruments through a reduction in both basic material costs and laborrequirements. Further, instruments produced in accordance with theinvention will provide the user great flexibility both in the ease ofreplacement of broken parts and in the simple method provided forconverting the angular relationship of a vial in a particular cell witha working surface of the instrument.

While previous level vials fabricated from plastic materials wereordinarily formed from extruded stock, the vials of the invention can bemanufactured utilizing high volume injection molding techniques. Aplastic vial material having a high degree of transparency, dimensionalstability and workability can be used to produce injection molded vialbodies in accordance with the invention. Such vial bodies can beproduced in great quantities at a relatively very low unit cost sincethe equipment used is capable of high volume production with a minimumof repair, replacement and maintenance.

The vial body of the invention is ordinarily fabricated from aninjection molded acrylic plastic. Although a wide variety of plasticmaterials are available as potential level vial stock, acrylicthermoplastic polymers of butyr ates such as cellulose acetate butyrateare presently preferred because of their degree of transparency; theirdimensional stability under broadly varying conditions; and theirworkability under the stress of high speed produc tion techniques.

The central portion of the interior of the body is generally providedwith a cylindrical bore. A pair of parallel annular grooves can be cutinto the external periphery of the vial body at a position spacedequidistantly from the midpoint of the bore portion of the vial. Thesegrooves serve as bubble alignment indicator guides. Generally,cylindrical vial end portions establish communication between thecentral bore portion and the exterior of the vial and providecylindrical sealing regions at the ends of the vial body. The exteriorof the tube is ordinarily provided with precision formed end portionsdesigned for close fitting engagement with precision preformed vialreceiving slots in the body of a level instrument.

In the preferred method of manufacture, a precision formed injectionmolded core member or pin is formed for introduction into the boreportion of the vial body. The core member is formed as an elongatedgenerally cylindrical member having an enlarged coaxially disposedcylindrical cap portion at one end thereof and a centrally locatedperipherally continuous concave portion formed between the ends of themember. This core member or pin may be provided with a pair of spacedbubble alignment indicator guide lines or grooves which can be cut intothe periphery of the core member at a location which will space thegrooves equidistantly from the midpoint of the bore portion of the vialbody when the core member is installed. These indicator lines maysupplement or serve to replace similar grooves formed on the externalperiphery of the vial body. The provision of indicator guide grooves orlines on the core member as opposed to the vial body will serve both toeliminate errors which can occur through optically produced parallaxdistortion when the bubble location of the level vial is read from theside and to allow protection of the indicator guide lines or grooves incertain mounting applications.

In assembling the cylindrical vial body and the core member to producethe level vial of the invention, the core member and cylindrical capportion is inserted into the larger cylindrical vial end portioncommunicating with the central bore portion of the vial. The tolerancesbetween the cap portion of the core member and the internal peripheralsurface of the cylindrical vial end portion are such that the coremember can be inserted into the end portion to form an essentiallyfluid-tight seal between the cap portion of the core member and theabutting vial portion. Also, the abutting surfaces of the cap portionand cylindrical vial end cavity serve an alignment function inestablishing the desired axial alignment of core member and vial bubblechamber.

A predetermined quantity of a fluid, such as a mineral spirit, isintroduced through an opening formed in the opposite end of thecylindrical vial structure after initial alignment of the core memberand vial. When this quantity of fluid has been introduced into thegenerally centrally located vial chamber, the core member is moved in anaxial direction until the end thereof opposite the cap portion entersand closes the fluid introduction opening formed in the vial body. Thisopening provides a secondary core member alignment element.

After the alignment of the core member has been established through itscomplete insertion into the cylindrical openings provided in the vialend portions which are resigned to accommodate the respective ends ofthe core member, a dimensionally stable adhesive or cement is applied toboth the vial ends and the exposed core member portions to bond theelements. The adhesive serves to hermetically seal the mineral spiritintroduced into the central vial chamber. In some applications, a secondadhesive may be applied over the first adhesive to provide a morepositive end seal of the fluid chamber.

When the assembly of the level vial elements and sealing thereof hasbeen completed, the core member is positioned in a manner such that itslongitudinal axis is coaxially located with respect to the longitudinalaxis of the generally cylindrical central bore portion of the vial body.The peripherally continuous concave portion of the core member ispreferably located between the cylindrical ends of the core member inthe completed level vial. The radius of the core member, atsubstantially the midpoint of the longitudinal axis of the portion ofthe core member located in the central fluid chamber of a vial, is apredetermined dimension. The dimension of the core member at selectivepositions spaced at intervals from the midpoint thereof and in eitheraxial direction are greater than the radial dimension of the core memberat the midpoint to control bubble registry in relation to apredetermined angular position of the vial With respect to a workpiece.

The construction of the invention will permit level readings to be takenat 360 around the level vial. This feature enhances the versatility ofthe vial in assembling it to a level frame.

Since the core member is introduced into the chamber of the level vialordinarily containing only a bubble forming fluid, the volume of liquidrequired to produce a bubble in the chamber is considerably reduced.This results in a substantial reduction in bubble size variations whichare ordinarily produced by temperature change.

Significant manufacturing economies can be realized 'With the level vialof the invention since the vial can be readily produced either fromstraight wall tubing stock or relatively simple injection moldingtechniques. The core member, depending upon the precision required forvarious applications, can be injection-molded, machined,precision-ground, etc.

Lower manufacturing cost and greater versatility can be realized withthe level vial of the invention since it is possible to form theperipheral concave portions of the core member with different radii ofconcave curvature while utilizing the same vial bodies. By varying theradius of curvature of the concave portion of the core member, thesensitivity of the completed level vial can be increased or decreased inproportion to the increase or decrease in the radius of concavecurvature.

The vial construction which embodies a solid core construction willprovide a more rigid structure which will be more resistant to damage orbreakage.

It is also possible, utilizing the vial construction of the invention,to use elements in color contrast in the assembled unit to facilitatereading. For example, the level vial can be formed with a colorlesstransparent body portion, a colored bubble producing fluid and either anopaque or transparent colored core member. Other variations arepossible.

Various other objects and advantages of the invention Will hereinafterbecome more fully apparent from the following description of thedrawings illustrating presently preferred embodiments thereof andwherein:

FIG. :1 is a fragmentary sectional view of a level vial made inaccordance with the invention and installed on the frame of a levelinstrument;

FIG. 2 is a cross-section of the vial and frame illustrated in 'FIG. 1and taken on lines 22 thereof;

FIG. 3 is a top plan view of a modified embodiment of the assemblyillustrated in FIG. 1; and

FIG. 4 is a side elevation of a level vial installed in the Web portionof a level instrument frame.

FIGS. 1 and 2 of the drawings illustrate an embodiment of a plasticlevel vial, generally designated 1, installed in the body or frameportion 2 of a conventional level instrument in a manner such as isillustrated in US. patent to Donald E. Wright, 3,311,990, which issuedApr. 4, 1967. As is best seen in FIG. 2, the level vial 1 of theinvention is positioned with the longitudinal axis thereof disposed inessentially the vertical plane of the frame 2 of the level instrument.

Referring now more particularly to FIG. 1, the body of level vial 1 iselongated along its longitudinal axis and includes an essentiallycylindrical bore or bubble chamber 3 which is located generally mid-waybetween the respective ends 4 and '5 of the vial body. It has been foundto be important to fabricate the plastic vial bodies from a plasticmaterial having a high degree of transparency, dimensional stabilityunder widely varying conditions and manufacturing workability. Suchmaterials will permit essentially the most economical production ofreliable level vial bodies. For best results, butyrates such ascellulose acetate butyrate, are preferred in the production of levelvials made in accordance with the construction of the invention.

As shown in FIG. 1, the vial body is fabricated with a first generallycylindrical bore portion 6 which terminates inwardly of the vial end 4at annular flange element 7 which is formed integrally with respect tothe vial body. The annular flange 7 defines an opening 8 which opensinto bubble chamber 3 and establishes communication between the bubblechamber and cylindrical bore 6. The opposite vial body end 5 is formedwith a second and slightly larger cylindrical bore portion 9 which alsoestablishes communication with bubble chamber 3.

A core member or pin generally designated 10, as shown in FIG. 1, ispositioned with the major .portion thereof disposed within bore orbubble chamber 3. Core member 10 is shown to embody an elongatedgenerally cylindrical member. This member includes first cylindical end11 positioned adjacent vial body end 4 and within and enclosing opening8 provided by annular flange 7. A second cylindrical end 12 of the coremember 10 is located adjacent vial body end 5. A generally cylindricalcap portion 13 is integrally formed on the second cylindrical end 12 ofthe core member. The outer periphery of the cap portion 13 is positionedin liquid-tight contact with the internal periphery of the secondcylindrical bore portion 9 at vial body end 5. The innermost end surface14 of the cap portion is positioned in abutting generally fluid-tightengagement with stop portion 15 defining the axial inner end of thesecond cylindrical bore 9. The core member is formed with a peripherallycontinuous concave portion 16 located between the cylindrical ends 11and 12 of the core member. The radius of curvature of the concavity ispredetermined according to the sensitivity required of the instrument ina particular application.

A pair of spaced apart indicator guide lines or grooves 17 and 18 areprovided on the external periphery of the core member 10 and are alignedin predetermined spaced relationship with respect to the axial midpointof the bubble chamber 3 and the axial midpoint of the portion of thecore member 10 located within the bubble chamber.

The generally cylindrical bore or bubble chamber 3 contains a liquid 19,such as one of the aliphatic hydrocarbons (commonly known as mineralspirits) or Stoddard solvents, in a volume insuflicient to completelyfill the bubble chamber 3. The volume of the liquid 19 introduced intothe bubble chamber is predetermined to produce a bubble or void in theliquid containing bubble chamber 3 of a desired volume. This bubble orvoid 20 acts as a measuring or gauging indicia in relation to the spacedannular guide lines or grooves 17 and 18 formed on the outer peripheryof the core member 10.

A primary liquid seal of the bore or bubble chamber 3 is produced at theend 4 of the vial body by the closure of the opening 8 by the firstcylindrical end 11 of the core member. The vial body end 5 of the levelvial 1 is provided with a primary liquid seal by the abutment of endsurface 14 of cap portion 13 upon stop portion 15 of the vial body andthe generally liquid-tight relationship of the cylindrical surfaceportion of the cap with the internal peripheral surface of the secondcylindrical bore 9. An essentially permanent and hermetic chamber 3 ofthe level vial is produced by the application of an organic adhesive orresinous mass such as an epoxy resin, in the first and secondcylindrical bores 6 and 9 adjacent the ends of the vial body.

In selecting the particular resin or organic adhesive to be applied asthe secondary or hermetic seal of the liquid containing vial, the epoxyresins have been found to be reliable. These resins fulfill one of themost important requirements of an adhesive system in that they provide ahigh degree of dimensional stability and are generally impervious tofluid components contained in level vials. They also cure withoutsignificant production of heat and permit relatively little air or gasentrapment. Such resins, therefore, minimize distortion of the vialshape and leakage of the fluid contained by the vial.

It has been found that organic adhesives or resins which containrelatively high percentages of evaporative solvents tend to develop asubstantial degree of resin shrinkage during the curing process as wellas excessive air or gas entrapment. Such shrinkage can readily cause adistortion of the bore portion adjacent the end to which it is applied,adversely affecting the gauging capabilities of the vial. Shrinkage caneventually lead to fluid leakage from the bubble chamber.

When the vial 1 has been assembled and sealed as illustrated in FIG. 1,the longitudinal axis of the core member 10, as can be seen in bothFIGS. 1 and 2, is aligned in essentially coaxial relationship withrespect to the longitudinal axis of the cylindrical bore or bubblechamber 3. It is preferred that the cross-sectional radius of the concave portion 116 of core member is smallest at essentially the midpointof the curved portion of member 10 substantially as shown in FIG. 2. Thedepth or radius of curvature of the concave portion 16 decreaseslaterally from this midpoint in both axial directions. The concaveportion 16, therefore, is formed with a predetermined radius ofcurvature, preferably formed in a manner such that the cross-sectionalradius thereof, at substantially the midpoint of the member 10 in thebubble chamber 3, is a predetermined dimension and the radius of theconcave portion at selected intervals along the longitudinal axis of thecore member 10' in either axial direction from this midpoint will beprogressively greater. It is preferred that the midpoint on concaveportion 16 is aligned substantially in the cross-sectional plane of themidpoint of the bubble chamber 3.

In the assembly of the level vial elements of the invention, the coremember 10 is initially inserted through the second cylindrical bore 9 ofthe vial body. The insertion of the core member is continued until thecap portion 13 thereof is brought within the confines of bore 9 with theperipheral cylindrical surface thereof located in essentiallyliquid-tight, although sliding engagement with the peripheralcylindrical surface defining the second cylindrical bore 9. Thisinsertion also acts as the primary alignment step in establishing thecoaxial relationship of the core member and bubble chamber. At thispoint, the first cylindrical end 11 of the core member is spacedcompletely below annular flange 7 and out of contact with opening 8provided thereby. The predetermined quantity of liquid 19 is thenintroduced through cylindrical bore 6 and opening 8 into bore or bubblechamber 3. When the predetermined volume of liquid 19 has beenintroduced into the bubble chamber 3-, the axial insertion of the coremember 10 is continued until cylindrical end 11 projects into opening 8into essentially fluid-tight contact with the wall of annular flange 7defining opening 8 and until the internal end surface 14 of cap portion13 of the core member is brought into abutting contact with the stopportion 15 of the vial body. At this point, the angular and axialalignment of the vial elements are established and upon sealing of theends thereof. the level vial is ready for use.

The core member 10 secured within the bubble chamber 3 of the level vialof the invention is constructed to control the location of the bubble inrelation to the indicator guide lines or grooves in accordance with apredetermined orientation of the longitudinal axis of the level chamberand core member. The construction of the core member is such that theperipheral edges of the bubble will be located essentially exactlybetween the spaced apart indicator guide lines when the predeter- 6mined angular relationship of the axes of the core member and bubblechamber has been established by either a working surface of the vial ora working surface of a level instrument in which the vial is secured andin relation to a surface being guaged. The radius of curvature of theconcave portion 16 of the core member 10 causes the bubble 20 containedin the bubble chamber 3 of the vial to be centrally oriented in thebubble chamber when the longitudinal axis of the core member is alignedin a predetermined relationship with respect to a surface to be guaged.The displacement of the bubble 20 from between the indicator guide linesor grooves framed on either or both the vial or the core member isproduced when other than the predetermined angular relationship betweencore member longitudinal axis and guaged working surface is established.This will cause the bubble 20 to move either towards end 4 or end 5indicating improper level alignment. As the radius of curvature of theconcave portion 16 of a core member 10 is increased, the sensitivity ofbubble registry is proportionally increased and smaller increments ofangular misalignment between the longitudinal axis of the core memberand the surface being guaged will produce a more pronounced bubbletravel to one end or the other level vial. Correspondingly, a decreasein the radius of curvature of the concave portion 16 of a core memberwill decrease the sensitivity of the level vial and bubble movement inthe bubble chamber 3 of the vial will be less pronounced with angulardeflection of the unit. In the event that no concave portion was formedin the core member or that the core member was completely eliminatedfrom the vial structure, the cylindrical surfaces defining the bubblechamber 3 of the vial would make it substantially impossible toaccurately control the position of the bubble in the chamber in relationto any angular relationship between the vial axis and a surface to beguaged. The result of such a structure would be the haphazard and randomorientation of the bubble in the chamber which would be substantiallyuseless for measurement purposes of any kind.

The level vial illustrated in FIG. 3 constitutes a slight modificationof that illustrated in FIG. 1. In this instance, the indicator guidelines or grooves 21 and 22 are cut into the external periphery of thegenerally cylindrical level vial body, generally designated 23, and areomitted from the core member 10 thereof. As is shown, these indicatorguide lines or grooves are formed in the periphery in the vial body 23and in coaxial relationship with respect to the longitudinal axis of thevial body and, particularly, the longitudinal axis of the bubble chambercontained thereby. While this modification of the level vial of theinvention may be employed in many applications and will accuratelyregister the position of bubble 20 with respect to the guide lines 21and 22 which are located to indicate a predetermined angularrelationship of the longitudinal axis of the vial with respect to aworkpiece, the guide line could be provided on both elements of thevial, as desired.

While the level vial of the invention is capable of being used inapplications where the vial is installed on a frame element of a levelinstrument and subsequently adjusted to bring the longitudinal axis ofthe vial into a predetermined angular alignment with respect to theworking surface of the level instrument, for example, in a manner suchas is shown in the US. patent to Ziemann 2,810,206, it is preferredthat, at least, a portion of the ends 4 and 5 of the level body areformed in concentric relationship with respect to the longitudinal axisof the bubble chamber and the core member. With these concentric orcoaxial external vial portions, the vial ends 4 and 5 can be alignedwith a pair of precision formed notches 24 and 25 spaced in opposedrelationship on level frame 2 as shown in FIG. 4. The vial may be movedat essentially a right angle to the plane of the frame 2 to bring thevial into precision, close-fitting engagement with the notch definingsurfaces. The disposition of the vial at this stage of assembly is suchthat the longitudinal axis of the bore or bubble chamber 3 and the coremember are aligned in parallel relationship with respect to the plane ofthe frame 2 as shown in FIG. 2. Essentially no further angularadjustment of the vial 1 is required although some lateral movement ofthe vial 1 with respect to the plane of the frame 2 may be made, ifdesired, and protective cover plates (not shown) may be applied over thelevel vial on opposite sides of the frame.

As is shown in FIG. 4, additional precision-formed and aligned notches26 and 27 may be provided in the frame of a level instrument to permitthe vial to be selectively disposed at other angular relationships withrespect to the working surfaces 28 and 29 of such a level instrument.

In producing level vials according to the invention, the cross-sectionalconfiguration of the bore or bubble chamber 3 and the cross-sectionalconfiguration of the exterior of the vial body can be varied as requiredprovided that the longitudinal axes of both the bubble chamber 3 and thecore member 10 are maintained in substantially coaxial relationship.

I claim:

1. A level vial comprising a body, the body being provided with acylindrical bore having opposed ends, a member disposed within thecylindrical bore of the body and between the ends thereof, the memberconstricting the space between it and the bore forming surfaceprogressively more at points further away from the intermediate portionof the bore, a quantity of fluid disposed within the bore, meanshermetically sealing the fluid within the bore, the quantity of fluidhermetically sealed within the bore being insufficient to completelyfill the bore thereby providing a bubble therein, the bubble being of asize sufiicient to simultaneously contact the bore forming surface andthe member, and indicator means for indicating a preselected position ofthe bubble with respect to the leveling surface and the member, the bodybeing transparent at least in a portion adjacent the indicator means topermit visual observation of the bubble with respect thereto, the memberbeing disposed to co-act with the cylindrical bore surface to produceprogressive bubble constriction therebetween as the bubble is displacedfrom its preselected position relative to the indicator means.

2. The level vial of claim 1 wherein the bore is an elongated cylinderand the member provided within the bore is elongated and has thelongitudinal axis thereof disposed in parallel relationship to thelongitudinal axis of the cylindrical bore.

3. The level vial of claim 2 wherein the intermediate portion of themember disposed between the portions of the member adjacent the boreends is coaxially disposed with respect to the longitudinal axis of thecylindrical bore.

4. The level vial of claim 3 wherein the coaxially disposed portion ofthe member is in longitudinal section a generally peripherallycontinuous concavity, the radius of the member at substantially themidpoint of the longitudinal axis of the member disposed within the boremeasured in any plane containing of the bore being a predetermineddimension, the radial dimension of the member at selected positions inthe said plane spaced at intervals from the midpoint and in eitherdirection with respect thereto being greater than the radial dimensionat the midpoint to produce progressive bubble deformity as bubbledisplacement from a normal position within the bore occurs.

5. The level vial of claim 3 wherein the bore is a circular cylinder,the member is coaxially disposed with respect to the longitudinal axisof the circular cylindrical bore, and the outer peripheral surfaceportion of the member disposed within the bore is disposed in concentricrelationship with respect to the longitudinal axis of the bore.

6. The level vial of claim 1 wherein means are provided at one end ofthe bore to align the member in predetermined relationship with respectto the longitudinal axis of the bore.

7. The level vial of claim 1 wherein means are provided at least at oneend of the bore for introducing fluid therein and means are provided tohermetically seal the fluid introducing end of the bore, the fluidintroducing means being disposed to provide a means for aligning an endof the member with respect to the body surface defining the bore.

8. The level vial of claim 7 wherein the member comprises an element ofthe hermetic sealing means.

9. The level vial of claim 1 wherein the bore opens fromopposite ends ofthe level vial body and wherein the member is both located in apredetermined relationship in the bore by the open ends and serves as aclosure of the open bore ends.

10. The level vial of claim 1 wherein the intermediate portion of themember is in longitudinal section formed with a generally peripherallycontinuous concavity and the concavity is formed with a predeterminedradius of concave curvature in accordance with the sensitivity ofmeasurement required of the level vial.

11. The level vial of claim 1 wherein the indicator means include linesprovided on the member to reduce parallax distortion in levelingoperations.

12. The level of claim 1 wherein at least a portion of the body and themember are made in color contrast to facilitate reading of the bubbleposition in the bore portion of the vial.

References Cited UNITED STATES PATENTS 612,577 10/1898 Smith 33211771,803 11/1904 Bishop 33-211 1,654,248 12/1927 Erdmann 332ll 3,020,5062/1962 Remington et a1 33-206 LEONARD FORMAN, Primary Examiner C. E.PHILLIPS, Assistant Examiner

